Telephone or like impulsing system



Sept. 12, 1944. D; A. CHRISTIAN TELEPHONE OR LIKE IMPULSING SYSTEM Filed Oct. 7. 1942 INVENTOR. DAVID ADAM CHRISTIAN BY a i 4 ATTORBEY Patented Sept. 12, 1944 TELEPHONE OR OFFICE DavidAdam Christian, Bat les, Englaniassignor t Siemens Brothers.& '00. England, a British company Application October '7, 1942, Serial No. 1 In Great Britain October-31, 1941,

Limited, London,

29 Claims.- (01.179-16) i This invention relates to telephone and like impulsing systems in which impulses are trans mitted as makes and breaks'in the impulsing circuit.

When impulses are transmitted over an im pulsing circuit, such as a line, they are subject to distortion of the make to break ratio. due to the electrical characteristics of the circuit and Where a route consists of two or more of such circuits connected in tandem the. distortion becomes accentuated and if the impulses are repeated from point 'to point the distortion becomes cumulative and may reach such dimensions that proper responseof theapparatus at the distant end is uncertain.

To this endproposals hav been made Wherein impulses, when 'repeated,are-repeated in a corrected form, either by recording the received impulses and generatin and transmitting new and perfect impulses, or by applying a' correction to received impulses which determines a inimum of maximum duration for the make and/or break of the impulses. V The present invention provides impulse modifying arrangements whereby the form of the impulses transmitted or received can be modified to give repeated impulses a desired form, that is, a desired make to break ratio, which permits of the introduction of a correction to compensate for any ratio distortion of the impulses during their transmission from point to point.

In the present invention impulse modifying arrangements are provided permanently associated with the impulsing circuit and comprise apparatus which is adapted to provide a fixed increase or decrease in the length of the make or break component :of an impulse as delivered to the arrangements with a corresponding alteration of a break or make so that the impulse as repeated by the arrangementshave a desired make-to-break ratio. The modification can be applied at the receiving point by modifying the impulses received thereat to have the desired make-to-break ratio, or alternatively the modification can be made at the transmitting end of the circuit so that the modification is entirely, or to a desired extent, nullified on the impulses reachin the receiving end.

The fixed modification may take the form of a retardation'or hastening of the operation and/or release of an impulse responsive relayor relays by a predetermined amount by Which a fixed period is subtracted from or added to the time during which a relay is operated consequent on .the receipt of an impulse which determines the I length of one of the componentsof a repeated impulse. This may be accomplished by a single relay Which may have-its operation or release delayed'either to 'shorten or lengthen acomponent of the repeated impulse. Alternatively itmay' beaccomplishedby a pair of relaysfone of which is delayed in operation and theother delayed in its release to brin g' about'the' said shortening 0r lengthening of the repeated impulse. rr v The delay in operation of a. relay is conveniently' accomplished by means of=an impedance in series with the operating coil of, the relay, and the delaying effect of the impedance may be controlled by a .resistanceshunted across it, the re- V sistance preferably being adjustable to enable adjustment-tobemade; V

-The delay in relea'seof a relay may conveniently beaccomplished by means of a condenser which is; charged or discharged for the duration of the component prior to-that to berepeated,

and when the component tobe repeatedfollows,

the condenser is connected to be discharged, or charged,' in a circuit which acts to assist the operatin coil, it beingv arranged that the discharge, or charging, current persists after the termination-of the impulse component to maintain therelay operated fora period equivalent to the modification to be made; A resistance is preferably connected in the charging, or discharging. circuit to det rmine the rateof charge, or, discharge. A similar arrangement can be used to delay the operation of the relay, the charge or discharge circuit of the condenser being con- 5 nected up on the commencement of a component to-be repeated, so asito, act in operating coil of the relay. f v 7 The fixed modification as applied is adjusted atone speed of impulsing but being fixed is in dependent of any variation in'the speed of imopposition to the pulsing. The modification may be predetermined andset so that the. desiredv ratio of make-to;

break is repeated. ..Thi predeterminationimay be carried out by transmittingimpulses of ado;- sired make-to break raticz over-the impulsing circuit and adjusting: the modifying arrangements at the'incoming. end of the circuit until the repeated impulses have the. desired ratio. Alternatively the modifying arrangements may be associated with :the'outg'oing end ofithecirwit and impulses ofa .modified ratio transmitted, themodified ratiobeingyaried until the impulses received at the incoming and of the circuit have the desired ratio.

In order to compensate-fora variation in speed iary modification dependent on the duration of r the components of the impulses may be applied,

the fixed and auxiliary modifications being added algebraically in the impulse modifying appa ratus. This auxiliary modification may be ap-' plied by means of an auxiliary relay theoperating or releasing times of which are hastened or delayed to add algebraically the requisite amount to the fixed modification. Such a relay is given a delay period under normal conditions of rope-'- tition, that is, where no auxiliary modification is required, so that to make an auxiliary modification its operation may be hastened or further delayed. Under such normal conditions its re leasing lag should equal its operating lag. The delay in operation may be accomplished by means of an impedance in series with the operating coil of the relay; and in its release'by meansof a-condenser arrangement, as previously referred to in connection with the fixed modificat Y 1 As the auxiliary modification requiredis dependent 'onj'speed; it is convenient to determine the auxiliary modification by measuring one of the components of an impulse, preferably the break, as actually received and with the fixed modification algebraically added to 'it and compare this with a corresponding correct component at the speed atlwhich the fixed modification wasmade, the auxiliary modification to be made depending on theexcessof theformer over the latter. i H m This may be accomplished by the use of a con 'stant period relay 'which 'is given' a delay ifi'operation equal to thebreak component'ofan impuls -at the speed at which the -fixed modificationiiwas made, that jisfas will'be repeated at this speed after the fixed modification'has been made, the relayoperating atthe endof this period and remaining operated during the said excess period to determine the auxiliary modification tobe brou'ghta'bout. The delay inoperation of the constant period relay may be imposed by a series impedance which may be regulated by a res'istanceshunting it. i

In the case where m V modifieja'tion to bring;v about a shortening of'the repat'ed make component and a lengthening of the break component by a requisite amount, the operating lag of the auxiliary relaymay be increased. jThisis conveniently accomplished by Q the use of a condenser which is charged during a make period through a coil of the auxiliary relay acting in opposition to the operating coil thereof; the condenser ,during the preceding ,lbreak p'eriod being discharged an amountfde- 'pendin'g 'on the aforesaid excess of the break period, c. -g. by theuse of the constant period relay. 'During the subsequent make-period as the charging, circuit forithe condenser includes a differential coil ,of the auxiliaryrellay, the operaftion'ot'the relaywvill be delayed an amount de- -'pending-on'the time it takes for the opposition to :be overcomeby the u e t Passing u h operating coil of therel ay e In the case where it is desired bythe auxiliary modification to bring about ashortening of'the break componentjanda'lengtheningof the make component, the operating lag er the auxiliary relay may be decreased, and a convenientwa'y I toj accomplis h thisjis to dlayftha operationby it is desired by the auxilan amount depending on the aforementioned excess period. The decrease in the operating lag may be accomplished by producing a flux in an impedance connected in series with the operating coil of the relay to an amount depending on the said excess period so that the impedance is less when'the operating circuit is closed, producing a consequential quicker operation of the relay.

A further manner in which to bring about the auxiliary modification is to provide the auxiliary relay with a coil in addition to its operating coil which additional coil is arranged to act either to assist or to delay the operation of the auxiliary relay for a period equivalent to the auxiliary 15;

excess period and during the subsequent make period be caused to discharge in one or other direction through the additional coil either to oppose or to assist the operation of the relay by an amount dependent on the value. of the charge, that is,on the excess period.

In a further manner of applying the auxiliary modification in'the aforementioned arrangement employing a pair of relays to effectthe main correction, condensers may .be employed which are adapted to be charged (or. discharged) during the break and make periodsof areceived impulse respectively, and connected in. a discharge (or charging) circuit, either to delay the opera.-

tion-of the said one relay or the'release of the said other relay. V In -order to enable the adjustment of the arrangements there may beprovided atthe end of the circuit from which the :impulses-aretransmitted animpulse sending arrangement which'i's adapted to'deliver impulses at a predetermined 'In the accompanying drawing, in Figs. 1 to 3,

are illustrated by way of example several ways in-which the above and'oth'er features not previ- "ously mentioned may be carried into efiect, the

arrangements of the several figures being described in'the following description. The arrangements are described and illustrated as associated with 'an impulsing circuit comprising a linebetween two telephone exchanges, the arrangements being use'dto apply a modification or correction to the impulses as received and distorted by theimpulse distorting characteristics'of the impulsing circuit whereby the impulses repeated at the receiving endha've substan'tially the same ratio as the impulses originally transmitted 'from the transmitting end. -Asfin the following arrangements the modification of "the impulses is in the nature of a correction, the latter term'will be used throughout the description.

-In'I 'ig'. '1 of the drawing the apparatus shown in the rectangle enclosed by the dot-dash line at the top left-hand corner represents a portion of theCapparatus at the outgoing exchange OE 'from whi-chfthe impulses are transmitted to the incoming" exchange IE over the junction line JCT. The apparatus in the transmission cir cuit at the exchange OE is as employed in known 7 tery-iconnection to the incoming loop practice and therefore only that part of the apparatus necessary to enable a complete understanding of the invention is shown and a general description thereof given. This apparatus is shown as an impulse repeater circuit comprising a repeater coil transmission bridge to the incoming side of 'which is connected an impulse relay A over-contactsdol anddoZ of abridge relay DO connected to the outgoing side of the bridge and to the junction JCT over contacts ao of the impulse relay and contacts haol and M02 of a-switching relay which is operated when a I preceding selector switch'tests into the free impulse repeater circuit. Contacts cc of a relay which is operated at the first impulse break and thereafter remains operated throughout the remainder of the impulse train, are adaptedto short-circuit the outgoing side of the bridge to give a clean impulsing loop during impulse repetition by the contacts a0. These latter contacts do in their normal position also short-circuit the outgoing side of'the bridge, the object being to provide a circuit which absorbs inductive surges from the repeater coil on the relapse of contacts ao during the first impulse repetition to prevent the induction of currents in the in coming side of the bridge'which may interfere with the performance of relay AO. Thesecontacts do have a resistance-and a capacity in series shunted across them to prevent sparking thereacross. The outgoing side of the bridge is connected via intermediate distribution points (not shown) in the exchange to a main distribution frame'where it is connected over a. heat-coil and arrester unit MP0 to the junction line JCT.

This unit MFO is of the usual kind and, in efiect, comprises break-jack points into which a test plug orshoe. TS may be plugged to isolate the connections internal and external to l the exchange and connect them to some testing apparatus.

The operation of the apparatus thus far described is, in general, as follows. When the repeater circuit is seized by a preceding selector switch, relay A0 and the switching relay controlling contacts hao operate, the former relay over the preceding loop and thelatter consequent on the operation of a slow relay by the operation of relay A0. The outgoing side of the repeating coil is thus looped across the junction JCT in series withjrectifier MRA to the distant exchange where it meets battery connections, the direction of connection of the rectifier MRB in series with the relay DO being such as 'to prevent current flow through relay DO with the battery conditions now prevailing. Relay A0 responds to the incoming impulse train and by its contact a0 repeatsthese impulses to the junction JCT and the distant break a slow-releasing relay controlling contacts 00 operates, and remains operated for the remainder of the impulse train, the contacts c0 short-circuiting the outgoing side of the .re-

peater coil and thereby providing a clean im pulsing loop to the distant exchange. On the ,cessation of the impulse train the contacts co relapse, and after the connection has been completely set up and the called party answers, the battery conditions on the junctions are reversed and; relay DO'operates inseries withrectifier MRB, the rectifier MRA no'longer being effective, and at its contacts dol anddo2 reverses'the batexchange. On the first circuit is opened. On

:rz'Z andthus to apply makes and breaks to the contacts.

supervisory operation such as metering. I It is desirable for testing purposes, as will be referred to later, to provide arrangements whereby impulses of a-desired speed and ratio can be transmitted from the exchange OE to the exchange IE. This may be done by means of a mechanical device such as an impulse 'senden-or it may be done by purely electrical arrangements as represented in the broken line enclosed rectangle These arrangements terminate, over a flexible cord, in a plug or testjshoe TS, so that they may be connected to the junction line JCT by plugging into the main frame-unit MP0. The testing equipment shown comprises an impulsing relay XA and an interruptingrelay XI. Contacts ml of relay XA are adapted to apply a loop'to the junction line on the operation of the relay, and shunting these contacts are a condenser QE and resistance RS in series, provided to simulate the capacity and resistance shunt across contacts (10, that is, to prevent sparking that may occur at contacts cral on opening, and also to dissipate any surges that may occur in the line'on the opening of the Contacts :cdZ control a ratio measuringl'meter XM for indicating the ratio of make to break of the generated impulses, the meter having an adjustable resistance R9 in series with it.

The relay XI has two windings connected in parallel with each other, one winding (the right hand) having a condenser QD connected in series with it. The ratio of make to break and speed of the impulses delivere'd'by the equipment depends upon the times of operation and release of relay XI which are determined by the capacity-of condenser QD. The apparatus is started in operation by throwing key XSK which at contacts XSKZ closes an obvious circuit for relay XA over contacts as?! and relay XA- oper ates. Contacts ital close'the" loop circuit, and contacts :ca2 the circuit for the ratio meter XM as before described. I I Contacts XSKI close the circuit for relay XI over self-interrupter contacts $21 of the relay. The operation of relay XI is delayed in operation by the condenser QD for two reasons, that is, it delays the building up of hand operating winding of the relay, andfurther, the direction of the charging current for the condenser through the right-hand winding of the relay is such as to oppose the effect of current flow in the left-hand Winding; :When the charge in the condenser has built up to a particular value, relay XI operates, and in doing'so interrupts itsown operating circuit at'contacts mil whereupon condenser QD discharges through both windings of relay XI 'in series in such a direction that the windings aid each other, the re lay being maintained operated 'in this manner for a predetermined period after its operating the relapse of the relay its circuit is again closed and'the'operations repeat ed solong as key XSK' is operated. Relay XA is made to follow the relay XI by means of contacts loop circuit ina predetermined ratio. 'An ad} justment for speed can be obtained by varfing the capacity of. condenser QD. I At the exchange IE the junction is connected through an arrester unit 'MFI, and further intermediate distribution points (not shown) at thatexchange toth'e ap' 1 paratus' which is shownias an impulse repeater comprising a repeating coil-transmission bridge the current in the left 7 substantially identical with that provided at exchange OE with the exception that the impulse relay AI does not directly repeat the impulses'to the outgoing side of the bridge, but only does so indirectly through impulse correcting apparatus. The outgoing side of the bridge may forexample extendto a selector at a local exchange or directly to a further junction line or over a junction selector.

The correcting apparatus includes a relay AA which controls an auxiliary relay AB, contacts ab2 of the latter being included in the outgoing circuit from the repeater circuit. The relay AA is included in a circuit which is adjustable to correct for the main impulse distortion characteristics of the junction, whilst the auxiliary relay AB is included in an auxiliary correcting circuit which corrects for the distortion introduced by a variation from a predetermined speed of the speed of impulsing. These arrangements will be described in detail together with the impulse generating and testing equipment TEI after the general operations have been described.

When the junction line JCT is taken into use at the preceding exchange OE, the loop applied from the latter completes the circuit for relay closed over contacts birl and ail, coil (I) of the impedance coil RAI, and relay AA, and this re-. layoperates. On the operation of relay AA a of impedance coil RA2 and left-hand coil of relay AB and relay AB operates. A loop to the circuit ahead is thereupon closed over contacts hi4, coils ,of repeating coil in series with rectifier MRC, contacts 0172, M2 and hi3 and the circuit ahead is taken into use. Relay -DI does not oper-" ate as the rectifier MRD is non-conducting to I current in the direction obtaining, and rectifier MRC shunts the relay.

Relay AI responds to the impulses transmitted from exchange OE and repeats them to relay 'AAat contacts ail. Relay AA in turn repeats the impulses to relay AB which at contacts ab2 repeats the impulses to the circuit ahead. On the relapse of relay AI to the break portion of the first impulse relay CI is operated in a circuit over contacts az2 and bid. Relay BI is the usual release relay and remains operated throughout the break portions of the impulse train and relay CI, due to its being slow to release remains operated throughout the make portions, being energised at each break, and releases at the end of the train. At contacts cz'2 an obvious circuit is closed for the supervisory lamp SY the purpose of which will be referred to later. oil the outgoing side of the transmission bridge is short-circuited to. provide a clean impulsing loop ahead. 7 V 7 When the distant party answers, the direction of current'over the positive and negative conductors is reversed and relay DI operates. At contacts 11! and di2, the battery connectionsto .the preceding circuit over relay A1 are reversed,

speed of impulsetransmission may consist of a lengthening or-a shorteningof the make period of a circuit is closed over contacts bir3 aa. 2, coil (I) At contacts resulting in the operationof relay DO at -ex- 7 change OE as previously described.

The distortion of impulses'durmgtransmission overan impulsing circuit at anyone particular an impulse and a corresponding shortening or lengthening, respectively, of the breakperiod according to the characteristics of the circuit. This distortion is referred to hereinbefore and after as the main or fixed distortion. To correct for this distortion a main or fixed correction is applied.

Distortion is also likely to occur due to variation of the speed of impulsing, such a variation of speed occurring owing to the difiiculty of ensuring that the several impulse transmitting apparatus from which impulses are likely to be received all transmit impulses at a nominal speed of impulsing. For example, in the case of a decrease of speed both make and break periods of an impulse are lengthened beyond that obtaining at anominal speed and with an increase of speed the components are shortened. To correct for this distortion a ratio or auxiliary correction dependent on the speed of impulsing or lengths of the components is called for.

Thus distortion through variation in speed of impulsing may be similar or opposite to the main or fixed distortion produced at one particular speed of impulsing. 7

It will be appreciated therefore that a fixed correction forcom'pensating for the main or fixed distortion of the impulsing circuit when considered alone can be made at any speed of im-. pulsing, preferably the average speed of impulsing, but when a variation in speed of impulsing is to be catered for it is desirable for the main or fixed correction to be made at one end of the range of anticipated impulsing speeds and an auxiliary correction for variation .of speed applied when the speed departs from this particular speed.

For this purpose in the particular arrangements described'and illustrated it is arranged that the auxiliary correction has its maximum efiect at a speed of impulsing different from that at which the main or fixed correction is made, and its minimum effect at the latter speed.

It is therefore convenient to make the main or fixed and auxiliary corrections at the olpopsite ends of the speed range likely to be met with. It is immaterial at which limits of this speed range the two corrections are carried out, but it is desirable that the auxiliary correctionapplied should be in the same sense as the variation of the length of impulses. This condition is obtainedif the main or fixed correction is made at a higher speed than the auxiliary correction.

pulses lengthen, and therefore be in an opposite sense.

In the arrangements to be described hereinafter it is assumed that the main or fixed correction is carried out at a higher speed of impulsing, e. g. 12 i. .p. s. than the auxiliary correction e. g. '7 i. p. s.

- In Fig. 1 of the drawing the main correction is carried outby means of animpedance coil RAJ, variableresistance RI shunting coil (I) of Ipeated make period takes this impedance coiLvariable resistance R2 shunting relay AA, condenser QA and resistance R6. The effect of coil (I) of impedance RA is to delay the rise of current in relay AA, the eflEect becoming less as the resistance RI is decreased. Resistance R2 and condenser QA delay the release of AA by an amount dependent on the value of resistance R2 and the charge existing in condenser QA. The condenser QA is fully charged over resistance R6 and contacts aal in their normal position (as shown) duringeach .break period, that is, at each relapse of contacts aal, resistance RB preventing sparking at contacts aal on their relapse.

To compensate for a gain in the make period of an impulse the valueof resistance RI is increased so thatits shunting effect on coil (I) of retard coil RAI is less-whereby the retard coil has a greater efiect in delaying the rise in current in the circuit for relay AA and the relay is caused to operate more slowly and delays the commencement of the repeated make period by a required amount. Resistance R2 is set at a maximum so that the delay in release .is negligible.

Where there is a loss in'the make period of an impulse, the adjustment required is to decreasethe resistance of RI and also that of R2 so as to increase the efiect of the discharge current QA through AA when relay AI releases at retard coil 'RB and'shunting resistance R4, to

have an operating lag equal to the break period the end of the make .period, resultingin a shorter operating period and an increased releasing lag of relay AA whereby a'lengthening of the replace.

The coil (II) of the retard coil RAI is wound differentially to coil (I). Thus at each release of relay AI, 0011- (II) of RAI is connected up over contact ail to-pr'oduce a magnetic flux opposite to coil (I), whereby any remanent flux is counteracted. In this manner it is ensured that the magnetic condition of retard coil RAI is the same at the commencement of each make period which in turn ensures that-the operating lag of relay AA is maintained constant for every impulse and is independent of the speed of impulsing.

' The value of the resistance R6 is such as to ensure that condenser QA is alwaysbrought to the same constant condition of charge at each break period. This will ensure that the release lag of relay AA is maintained constant.

The auxiliary correction, which is carried out at a slower speed of impulsing than that at which the main correction is adjusted,-is accomplished by the circuit arrangement comprising relay AB and constant period relay AY, and other apparatus illustrated. The arrangement provides for'correcting a change in the gain or the loss in the length of the make period brought about mainlyby a decrease or increase in the speed of transmission of the impulses. The circuit arrangement is connected up to correct for a gain of make with the key K in its norm-a1 position, as shown, whereas the key is operated'eto correct for a loss of make. As both corrections include varying the operating lag of relay AB,

that is, either shortening or lengthening it, it is necessary that the relay should have considerable operating lag and so'that its effect is zero when correction is not necessary, the releasing lag should.be equal to the operating lag. The' operating lag is obtained by connecting the operating coil (left-hand coil) of relay AB in series with coil (I) of retardiRA2 shunted by a fixed resistance,R3. The release lag is controlled by condenser QB is charged to a constant value 'over a circuit including contactsaaii, key contacts KI, and the right-hand coil of relay AB When relay AA releases at the beginning of the breakperiod, the circuit of relay AY is closed over contacts bir3 .and (M12, and relay AB releases after itsslow to release period imposed by condenser QC to repeat thebreak to the circuit' ahead at contacts abZ. Relay 'AY operates at the termination ofa break period at the speed at which the main cor rector was adjusted and a discharge circuitfor condenser QB is'closed over contacts aa3, key

contacts K2, variable resistance R5, andcontacts ayl and birZ, the rate of discharge of'the condenser being determined bythe adjusted value of resistance R5. On the operation of relay AA at the commencement of the next make period, the discharge circuit is opened and condenser QB is again connected in circuit with the righthand coil of relay AB. The condenser QB, dis

charged an amount dependent on 'theexcssof the break period received over that atthe speed at which the main corrector was adjusted, com,-

mences to charge up'again and the direction of 7 the current flow in the right-hand coil ;of relay ABis such as to oppose'the main operating ;current and delays the operation of relay Al3- 'u'ntil the opposition becomes inefiective.- This delay in operation of relay AB'is thereforedependent on the lengthof the said excess.

The value to which the resistance R5 is adjusted depends upon'the amount of the distortion to be corrected. 1

To counteract a loss of make, thekeyK- is thrown "to its operated positionf In this-case it is required that the operation of relay AB shall be hastened, and in order to do this the impedance of retard coilRAZ is reduced by an amount of premagnetisation dependent on the said ex- .cess of the preceding break period. To accombe slow inorder that the required amount of premagnetisation corresponds to the excess break.

This is done by the use of the retard HA3, the two coils of which are connected to act in oppositionto each other. During the make period and during the period corresponding to a'break' period at the speed at which'the main corrector was adjusted, coil (II) of retard RA3; is energised over contact bzrZ and'a'Jl to produce a magnetic flux in a particular direction.- When' relay AY operates at the end of the said break period, and whilst it remains operated throughoutthe excess break period, a circuit isclosedover resistance R5 adjusted to a position depending on the During the make periodpreceding the break,

,XB-T at contact The test plug TS at exchange independently of contacts average to be correction to be made, key contact K2 (operated) coil (I) of retard RA3and coil,(lI)' or retard HA2. In this circuitthe'direction of current in coil (1) of retard RA3 is such as to produce a flux in opposition to that already built up by coil (II) and this delays the riseof current in coil (I) and in consequence in coil (II) of retard RAZ, the rate of rise also depending on the resistance R5. Therefore the value of the flux' existing in retard RAZ when relay AA again operates to the next make period is approximately proportional to the excess break period, and the time of operation of relay AB is lessened by an amount cor responding to this excess. Thus in effect a portion has been subtracted from the breakperiod and added to the make period asrepeated.

The apparatus enclosed in the broken line rec'- tangle TEI is an impulse generating and receiving equipment, generated impulses being delivered to a plug associated witha break jack BJ in the repeater circuit, whilst impulsesare accepted over a plug adapted to be-plugged into test jack TJZ This apparatus may be adjusted to simulate impulses as received over the junctionJCT. The operations involved in the generation of impulses of a determined frequency and ratioare as follows. Key YSK is. operated and a circuit is thereupon closed over contacts .YSK'I and til for relay YI which operates after a fpredetermined interval'as determined by the capacity of condenser QF (as described in connection with relay XI, at exchange OE). Also a circuit is closed over contacts YSK2 and upper con of relay XRT, and impedance IRA shunted by a resistance RH. Relay XRT operates after 'a lag :as determined by the efiects of impedanceXRA and resistance RH. On the operation of relay XRT an obvious circuit is closed for relay YA and relay YA operates. At contacts yal a loop'circuit is closed over the cord terminating plug which is adapted to be. plugged into break jack BJ. At contacts yaZ a loop is closed to. the points of a test jack TJ 3 which is to enable the ratio measuring meterito be directly connected to the contacts to indicate the manor the impulse s actually being transmitted. H V V 7 When relay YIoperates it disconnects'its own circuit at contacts y ,and' the circuit for relay yi2 V v .1 I I QF and resistance RIO in series e condenser across contacts yal are provided to absorb any surges that may occur across the contacts, and simulate the conditions oi-the impulse repeating contact at the outgoing end of the line JCT. 7

' The routine to be followed forsetting the main and auxiliary correcting apparatus is as follows. OEis plugged into the arrester unit lVLFfO, thus connecting the testing equipment TEO to the junction JCT; At exchange IE the plug associatedwith'the J'ac'k TJZ is inserted into the jack. V V withdrawn from test jack "TJ and inserted in test jack TJ4, thus disconnecting the circuit of relay BI and preparing the circuit'of relay. CI so that relayQI will operate on the release ofrelay Aland remain operated during thereception of impulses. As

ej-asejme age speed of impulsing is 10 impulses per sec., then TEO may be set to deliver 12 impulses per sec., the break-'to-make ratio at both speeds being the same.

The impulses are received by relay AI and repeated to relays AA and and thence over contactsab2 and test jack TJ 2 toth'e ratio'meter YM which has a regulating resistanceRlZ in series with it. The main correction is accomplished by adjusting resistances RI and R2 until the correct make to break ratio of the impulses is repeated at contacts 11122 as indicated by the meter YM.

When the requisite main correction has been made, the auxiliary correction is performed at a lower speed, for example, 7 impulses per sec. and the necessary regulation made for loss or increase of make by adjustingre'sistance R5 as will now be understood, I v

When the adjustments have been made the testing apparatus is disconnected from the junction in preparation for normal operation. When lamp SY is maintained to indicate that normal conditions have not been established.

If at any time it is desired locally to test the correcting arrangementsfor correct operation, the associated plug is inserted into the test jack BJ, as are also the plugs associated with jacks TJ I and TJZ; and the link L'is changed over tothe test jack TJ 4 asbe'iore. The junction JCT is isolated from the bridge at the break jack BJ and busy tone over wires ET is applied to the junction over the jack TJ l to indicate to a calling party at exchange OE that the junction is not available. The test can now be carried out by setting the testing equipment TEI to apply impulses to the correcting equipment simulating. those which would-be applied over the junction JCT as determined on previous tests. If anyvariations are indicated, a fulltest canagainbe carried out from the exchange OE.

Also the link L is relay BI cannot be operated any impulses received but in the same ratio. For example, if the avertransmitted over the junction JCT applied for-a g In Fig. 2 is illustrated a modification of the auxiliary correcting arrangement of Fig.1 the main difference being that the condenser QB, in-

stead of being partially discharged to measure the excess break period and controlthe delay or more rapid operation of relay'AB, receives a charge dependent on this excess break period and controls the relay AB accordingly.

The impedance RAZ in series with thelefthand operating coil of relay AB has only one coil.

The inherent operating and releasing lags of relay AB are determined in a manner identical with that described in connection with Fig. l.

The key K occupiesits normal position as shown) to correct again in the make period on a decrease in speed of impulse transmission, and is operated to correct a loss in the make period at a low speed of impulse transmission.

The manner in which an auxiliary correction is am in the length of the make period is as follows: When relay AY operates, a charging circuit for condenser QB is closed over contacts aa3, ayl and the series resistance R5. At

the termination of the break period when relay AA re-operates, a discharge circuit for condenser QB is closed over key contacts K2, upward through the right-hand coil of relay AB, key contacts Ki, and contacts cs3. The direction of this discharge current is such'a's to oppose the operating current in relay resulting in a delay in operation of the relay by an amount depending on the charge existing in the condenser, that is,

Jon the extent of the excess break period over the break period'at the speed at which the main correction was adjusted.

In the case of a shortened make period, the key K is thrown to its operated position. As before, during the excess break period condenser QB receives a charge to anamount dependent on the excess of the break period. At the termination of the break period when relay AA reoperates, a

discharge circuit for condenser QB is closed over key contacts K2, .downward'through the righthand coil of relay AB, impedance HA4, key contacts KI and contacts 11113. The current in this auxiliary corrections. As farras possible similar references are used to indicate parts carrying out functions similar to those carried out-by like parts in Fig. 1. In general the main and auxiliary corrections are carried out by the adjust ment of the operating lag of relay AA and releasing lag of relay AB. For obtaining the appropriate auxiliary corrections two keys AK and BK are provided, the key AK being provided for 'efiecting an auxiliary correction to compensate for an increased make period and key BK fora decrease in the make period at a low speed of impulsing.

As in Fig. 1 relay AA is caused to follow the impulse relay (AI) and relay AB to follow relay AA to repeat the impulses to the circuit ahead;

A main correction above is carried out with the keys AK and BK occupying their normal positions as shown. 1 r

In order to efiect a compensation in the make to break ratio of an impulse as received where the main distortion is such as to produce a lengthened make period, the resistance RI shunting the impedance coil RAI in circuit with the left-hand operating coil of relay AA is adjusted to delay the "operation of relay AA by the amount of the excess of the make period received over the make period to be repeated. 7

Conversely, to efiect compensation of the ratio where the main distortion produces a shortened make period the actions are as follows:

There is provided a condenser QC which during the time relay AB is'not operated, thatis during a break period, is charged in a circuit including resistance R], the condenser being fully charged during each break period. On the operation of relay AB at the end of the break period a discharge circuit for condenser QC is closed over the right-hand winding of coil AB, and the condenser discharges through this coil in such a direction as to assist the operating current. The resistance R3 is adjusted to determine the rate of discharge of the condenser QC so that the discharge continues after the termination of the make period of impulses as received'to maintain relay AB operated for a period equal to the amount to be added to the repeated make period.

Thus by adjustment of resistance R3 relayAB can be made to release more slowly ,than its normal release period by an amount corresponding to.the distortion of the break, period,

which amount is added to the repeated make periods.

The auxiliary correction to compensate for a lengthened make, is obtained by the operation of key AK alone. When this key is operated and during the break period of an impulse, condenser QA is charged over a circuit including contacts of key AK, contact at! of the impulse relay, and resistance R6 and condenser QA receives.

a charge depending on the length of the break period and the value to which resistance R6 is adjusted. When the impulse relay (AI) operates at the end of the break period, a discharge circuit for condenser QA is closed over the right-v hand coil of relay AA. The direction of this discharge current is opposite to the main operating current and the opposition results in a delay in the operation of the relay until such time as the effects of the main current overcome those of the discharge current, this period being arranged by the adjustment of resistance R6 ,to a value for determining the requisiterate of discharge to correspond'to the excess make period. I

In order to compensate for a decreased make period at a low speed of-impulsing, key BK is alone operated. In this case during a make periodwhen the impulse relay (AI) is operated, condenser QB receives a, charge depending on the length of the make period and the value of At the terminareleases, a. discharge circuit for condenser QB is closed over the left-hand coil of relay AB. The duration of this current is such as to produce a similar magnetisation of the relay as the operating current with the result that relay AB is delayed in release for a period until the discharge current falls below a value which will maintain the relay operated, this period, by the adjustment of the rate of charge, as determined by the setting of resistance R5, corresponding to the excess break. The effect, therefore, is to subtract a portion from thereceived break and add it to the repeated make. 7 It will be appreciated that the exemplary arrangements described above can be modified in that the correcting arrangements may be situated at the outgoing end of the junction, that is, at exchange OE. In this case, the correction in eifect, is a negative one which-is nullified by the impulse distorting characteristicsof the junction so that the impulses received at exchange IE will have the same mak to break ratio as the original impulses at exchange 0E and may directly berepeated in an undistorted form at exchange IE. The correcting arrangements as described above are suitable for this purpose.

What I claim as new and desire to secure by Letters Patent is: V

. 1. In a impulsing system, an impulsing circuit, means for alternately opening and closing said circuit thereby to generate impulses, each impulse having a make component and a break component, an impulse repeater permanently associated with said circuit for receiving and repeating said impulses, said repeater including means for causing the make component of each repeated impulse to be a fixed amount shorter than the make component of the corresponding received impulse and for causing the break component of each repeated impulse to be a fixed amount longer than the break component of the corresponding received impulse, whereby the than the make component of the corresponding received impulse and for causing the break component" of each repeated impulse" to be a fixed amount shorter than the break component of the corresponding received impulse, whereby the maike-to-break ratioof the-repeated impulses isdifferent than that of the received impulses.

3. In an impulsing system, a'line having an impulse responsive device connected thereto, an

impulsing circuit, means'for alternately opening and closing said circuit thereby togenerate impulses, each impulse thus having a make component and a break component, an impulse re- H 'p'eater associated with said circuit for receiving said impulses and repeating them over said line to said device, said repeater including means for causing one of said components of each repeated impulse to be a fixed amount longer than the same component of the corresponding received impulse and for causing the other component of each repeated impulse to be a fixed amount shorter than the same component of the corresponding received impulse, said line having electrical characteristics such as to nullify said repeaters modification of the impulses, whereby the impulses received by said device have the same make-to-break ratio as the im pulses generated in said circuit, 7

4. In an impulsing system wherein impulses are generated at different speeds at different times andsa id impulses consist of break and makes of an impulsing circuit, an'impulse repeater asso ciated with said circuit for receiving and'repeatin said impulses, said 'repeater including means functioning independently of the speed of the re- .ceived impulses for causing the make component of each repeated impulse to be a fixed amount longer than the make component of the corre sponding received impulse and-for causing the break component of eachrepeated impulse to be a fixed amount shorter than the break component of the correspondin received impulse, whereby the make-to-break ratio of the repeated impulses is different than that of the received impulses, a second impulse repeater connected to the output of said first repeater for receiving and repeating the impulses repeated by said first repeater, said second repeater including means for making an additional change in the make-tobreak ratio of the repeated impulses in accordance with the speed at which impulses are received by said second-repeater;

5. In an impulsing system wherein impulses are generated at different; speeds at different times and said impulses consist of breaks and makes of an impulsing circuit, an impulse repeater associated with said circuit for receiving and repeating said impulses, said repeater including means functioning independently of the speed of the received impulses for causing the make component of each repeated impulse to be a fixed amount shorter than the make component of the corresponding received impulse and for impulse to be a fixed amount longer than the break-component of the corresponding received impulse, whereby the make-to-break ratio of the repeated impulses is different than that of the received-impulses, a second impulse repeater con nected to the output of said first repeater for receiving and repeating the impulses repeated by said first repeater, said second repeater including meansfor makin an additional change in the make-to-sbreak ratio of the repeated impulses in accordance with the speed at which impulse are received by said second. repeater.

6. In an impulsing system, a circuit over which trains of impulses are. transmitted, each said impulse being divided into two complementary periods having a certain ratio to each other,'an impulse. repeater effective to receive. and repeat each. said impulse, said repeater including means for increasing one period of each impulse by a fixed. amount and for decreasing the other period of each impulseby a corresponding amount, whereby each repeated impulse is divided into two. complerrientaryv periods having a ratio to each other. different than said certain ratio.

7. An impulsingsystem as claimed in claim 6, wherein said means includes a relay and means for-varying theoperating time and release time of said relay.

8. In an impulsing system, a circuit over which trains of impulses are transmitted, each said impulse being divided into two complementary periods havin acertain ratio to each other and the successive ones of said impulses occurring at different speeds in difierent trains, an impulse repeater effective to receive and repeat each said impulse, said repeater including mean functioning independently ofthe speed of successive impulses for. increasing one period of each impulse by. a fixed amount, and for decreasing the other period of each impulse by a corresponding amount, whereby each repeated impulse is divided into'two complementary periods having a ratio to each other different than said certain ratio, a second impulse repeater connected to the output of said first repeater for receiving and repeating the impulses repeated by said first repeater, said second repeater including means controlled in accordancewith the speed of successiveimpulses for making an additional change in the ratio of said periods.

v 9. An impulsing system as claimed in claim 8, wherein said last means includes a relay and means for varying the operating times and release times of said relay.

causing the break component of each repeated 75 10 In an impulsing system, a circuit over which trains of impulses ar transmitted, each said impulse being divided into two complementary periods having a certain ratio to each other and the successive ones of said impulses occurring at different speeds in difierent trains, an impulse repeater effective to receive and repeat each said impulse, said repeater including means functionin independently of the speed of successive impulses for increasing one period of each impulse by a fixed amount and for decreasing the'other period of each impulse by a corresponding amount, whereby'each repeated impulse is divided into two complementary periods having a ratio to each other different than said certain ratio, a second impulse repeater connected to the output of said first repeater for receiving and repeating the impulses repeated by said first repeater, said second repeater including means controlled in accordance with the length ofone of the said periods of an impulse received by said second repeater for making an additional change in the ratio of said periods.

'11. In an impulsing system, anincoming circuit and an outgoing circuit, means for impressing spaced apart impulses upon said incoming circuit, a repeater effective responsive to the beginning of each impulse impressed upon saidincoming circuit to initiate the transmission of a corresponding impulse over said outgoing cir- "cuit and efiective responsive to the end of each impulse impressed upon said incoming circuit to terminate the transmission over said'outgoing circuit of the corresponding impulse, and adjustable means for varying the speed with which said repeater initiates transmission of an impulse over said outgoing circuit in response to the beginning of the corresponding impulse in said incoming circuit.

12. In an impulsing system, an incoming circuit and an outgoing circuit, means for impressing spaced-apart impulses upon said incoming circuit, a repeater efiective response to the beginning of each impulse impressed upon said in, coming circuit to initiate the transmission of a corresponding impulse over said outgoing circuit and efiective responsive to the end of each impulse impressed upon said incoming circuit to terminate the transmission over said outgoing circuit of the corresponding impulse, and adjustable means for varying the speed with which said repeater terminates transmission of an impulse over said outgoing circuit in response to the end of the corresponding impulse in said incoming circuit.

13. In an impulsing system, an incoming circuit and an outgoing circuit, means for impresscuit and an outgoing circuit, means for impressing spaced apartimpulses upon said incoming circuit, a repeater efiective responsive to the beginning of each impulse impressed upon said incoming circuit to initiate the transmission of a corresponding impulse over said outgoing circuit and effective responsive to the end of each impulse impressed upon said incoming circuit to terminate the transmission over said outgoing circuit of the corresponding impulse, adjustable means for varying the speed with which said repeater initiates transmission of an impulse over said outgoing circuit in response to the begin- .ning of the corresponding impulse in-said incoming circuit and other adjustable means for varying the speed with which said repeater terininates transmission of an impulse over said outgoing circuit in response to the end of the corresponding impulse in said incoming circuit.

14.. In an impulsing system, an incoming circuit and an outgoing circuit, means for impressing spaced apart impulses upon said incoming circuit, a repeater effective responsive to the beginning of each impulse impressed upon said incoming circuit to initiate the transmission of a corresponding impulse over said outgoing circuit and effective responsive to the end of each impulse impressed upon said incoming circuit to terminate the transmission over said outgoing circuit of the corresponding impulse, and means effective whenever the time between the end of one impulse impressed upon said incoming circuit and the beginning of the next impulse impressed upon said incoming circuit eXceeds a predetermined interval for reducing, in proportion to the excess, the speed with which said repeater initiates transmission of an impulse over said outgoing circuit in response to the beginning of said next impulse.

15. In an impulsing system, an incoming cirone impulse impressed upon said incoming circuit and the beginning of the next impulse impressed upon said incoming circuit exceeds a predetermined interval for increasing, in proportion to the excess, the speed with which said repeater initiates transmission of an impulse" oversaid outgoing circuit in response to the beginning of said next impulse. V I r 16. In an impulsing system, anincoming circuit and an outgoing circuit, means for impressing trains of spaced apart impulses upon said incoming circuit, a relay having its winding connected to said incoming circuit to render it responsive to said impulses-and having a contact connected to said output circuit to repeat said impulses thereto, and a variable impedance in series with the winding of said relay for adjusting the speed with which said relay operates said contact in response to the beginning of each impulse impressed upon said incoming circuit.

17. An impulsing system as claimed in claim 16, wherein said variable impedance comprises a fixed inductance element in, series with said relay winding and a variable non-inductive resistance shunting said element.

18. In an impulsing system, an incoming circult and an outgoing .circuit, means for impressing trains of spaced-apart impulses upon said incoming circuit, a relay having its Winding connected to said incoming circuit to render it responsive to said impulses and having a contact connected to said output circuitto repeat said impulses thereto, adjustable means vfor varying the speed with which said ,relay operates said contact in response to thebeginningof each impulse impressed upon said incoming circuit, and other adjustable means for varying the speed with which said relay operates said'contact in responseto the end of each impulse impressed upon said incoming circuit. V I

19. In an impulsing system, an incoming circuit and an outgoing circuit, means for impressing trains of spaced-apart impulses upon said incoming circuit, a relay having its winding connected to said incoming circuit to render it responsive to said impulses and having a contact connected to said output circuit to repeat said impulses thereto, a variable impedance inseries with the winding of said relay for adjusting the speed with which said relay operates said contact in response to the beginning of each impulse impressed upon said incoming circuit, and another variable impedance in shunt with the Winding of said relay for adjusting the speed with which said relay operates said contact in response to the end of each impulse impressed upon said incoming circuit.

20. In combination, an impedance coil having two windings; a circuit over which one of said windings is energized; contact means operated.

being so related to one another that the decay of current in said one winding responsive to the operation of said contact means opposes the increase of current in said other winding and hence delays the operation of said relay. 7 I

21. In combination, an impedance coil having two windings; a circuit over which one of said windings is energized; contact means operated to interrupt said circuit and, at the same time, to complete another circuit including in series a source of current, a relay and the other winding of said impedance coil; said two windings being so related to one anotherthat the decay of current in said one winding responsive to the operation of said contact means opposes the increase of current in said other winding and hence delays theoperation of said relay; a condenser; a charging circuit for said condenser; 'a contact controlled by said relay upon operation for interrupting said charging circuit and connecting said condenser in shunt to said relay; means for causing said contact means subsequently to interrupt said series circuit; said condenser thereupon being effective to discharge through said relay to delay the release of said relay.

"22, A combination as' claimed in claim 21, wherein the shunt circuit across said relay includes, in addition to said condenser, a variable resistor for, controlling the discharge of said condenser through said relay.

23. In combination, a relay, an impedance coil, a circuit including said coil and the winding of said relay, a source of current, means for alternately connecting said source to said circuit and disconnecting it therefrom, thereby alternately to operate and release said relay, means for subjecting said impedance coil to a magnetic field immediately prior to eah connection of said source to said circuit, and means for varying the strength of said field thereby to control the speed with Which said relay operates in response to the connection of said source to said circuit.

24. A combination as claimed in claim 23, wherein said last means causes the strength of said field 'to vary in proportion to the time in excess of a predetermined interval that said first means causes said source to remain disconnected from said circuit.

25. In combination, an impedance coil having two windings; a relay; means for completing an energizing circuit for one winding of said coil; means operated a variable interval'after said circuit is completed for completing another circuit including in series asou'rce of current, the other winding of said 'coil and the winding 'of said relay; said relay thereuponefiective to operate after a delay whose length depends uponthe extent to which said other windingwas premagnetized as a result of the prior completion of said first circuit.

26. In combination, two impedance coils each having two windings, 'a circuit over which one winding of the first impedance coil'isener'gized, means operated to interrupt said circuit and, at the same time, to complete a circuit including in series a source of current, theother winding of said first coil and one winding of the second impedance coil, means then operated "a variable interval of time after said last circuit is completed for completing another'circuit including in series a source of current, a'relay and the other Wind'- ing of said second impedance coil, said relay thereupon effective to operate after a'delay whose length depends upon the extent to which said other winding of said second impedance coil was premagnetized as a result of said prior operation of said first means.

27. In combination, a relay, impulse operated means for alternately opening and closing an energizing circuit for said relay, an impedance coil having one winding in said circuit to delay the growth of current therein upon each closure of said circuit, a second winding on said impedance coil, and means effective'if said energizing circuit remains open for apredetermined interval of time for thereupon completing a circuit for energizing said second winding, whereby upon the subsequent closing of said first circuit the effect of said impedance coil upon the growth of current in said first circuit is modified in accordance with the amount by which said first winding has been premagnetized by said second Winding.

28. In combination, a relay having two windings, impulse operated means for alternately opening and closing an energizing circuit for one winding of said relay, a charged condenser, means effective each time said energizing circuit is opened for discharging'said condenser an amount proportionate to the time, if any, that said energizing circuit remains open in excess of a predetermined interval, a charging circuit for said condenser completed over the other winding of said relay simultaneously with each closing of said energizing circuit thereby to restore to said condenser any charge removed from it prior to said closing, any charging current flowing through said other "winding being effective to oppose the flux generated by said one winding and hence delayingthe operation of said relay until the charge is restored to said condenser.

29. In'combination, a relay having two windings, impulse operated means for alternately opening andclosing an energizing circuit for one Winding of said relay, acharged-condenser, means "efiective each time said energizing circuit is DAVIDADAM CHRISTIAN. 

